By John FleckJournal Staff Writer
Gerhard Schoener calculates that, in its best month, the cistern that collects rain from the roof above his office captured more than 9,000 gallons of water.
The water is used to irrigate the landscaping at the offices of the Southern Sandoval County Arroyo Flood Control Authority, explained Schoener, technical projects specialist for the authority.
This corner of Rio Rancho counts as desert, averaging less than 10 inches of rain per year. Yet most of the water for the landscaping at the flood control agency's office comes not from city water pipes, but from the roof.
Out front, rainwater collects in a small pond, soaking into the ground rather than running off into the street. Volunteer desert willows are taking root in the bottom of the pond, and workers are preparing the space for more cisterns on a new wing of the building currently under construction.
"It's easy to do," said Kent Beierle, the architect responsible for the project.
In this arid climate, "rainwater harvesting," as it is called, would seem like a no-brainer.
"It's something that we should all do now as a matter of routine," Albuquerque landscape architect Rick Borkovetz said.
At first blush, it would seem the New Mexico Office of the State Engineer, the agency that manages New Mexico's water, agrees.
"The New Mexico Office of the State Engineer supports the wise and efficient use of the state's water resources; and therefore encourages the harvesting, collection and use of rainwater from residential and commercial roof surfaces for on-site landscape irrigation and other on-site domestic uses," reads a policy statement issued in 2004.
But this is the murky and sometimes contentious world of New Mexico water law, so you know there is going to be a catch: "The collection of water harvested in this manner should not reduce the amount of runoff that would have occurred from the site in its natural, pre-development state. Harvested rainwater may not be appropriated for any other uses."
That last bit is the complexity that faced water consultant Daniel B. Stephens recently as he tried to explain to a group of New Mexico water experts the value and pitfalls of rainwater harvesting.
Stephens thinks rainwater harvesting makes a lot of sense in a place like this, where water is scarce. But once you start to get more ambitious about what you want to do with the captured water, you run into trouble, Stephens explained last month at the Water Resources Research Symposium in Socorro.
Take the example of a small subdivision that gets its groundwater from wells, Stephens said. You could design a rainwater harvesting system that collects runoff from roofs and driveways and allows it to soak into the ground, recharging the aquifer.
Stephens calculates the subdivision could meet a quarter of its water needs that way.
It sounds great, but it runs afoul of the "any other uses" clause in the state policy, according to both Stephens and State Engineer John D'Antonio. Watering your plants, or even using the water to flush your toilet, is fine. But groundwater recharge crosses a line.
D'Antonio is the guy who is responsible to see that everyone who uses any water in New Mexico has a legal right to that water, and in his view a subdivision capturing runoff that would otherwise head downstream somewhere amounts to "appropriation," and is subject to state law.
This goes back to the first part of the state's policy: the rule that when you're capturing rainwater, you can't reduce the runoff that would have come off your property "in its natural, pre-development state."
In the strange world of water law, the portion of the rain and snow that falls on your property that would have run off before it was developed isn't yours. It belongs in a legal sense to the myriad water rights holders downstream from you. It can be used by farmers and cities that have a pre-existing right to draw water from the state's rivers and streams for their use. Or the water can be used to meet New Mexico's legal obligations under the Rio Grande Compact to deliver water to Texas.
Stephens thinks a lot of the water running off his hypothetical subdivision would end up evaporating. Using it to recharge the aquifer, he argues, means a net water savings.
I think of this every time I stand in my living room watching rain run off the driveway into the gutter during a thunderstorm, headed into Albuquerque's storm drain system and ultimately to the Rio Grande. I've got a rain barrel in the backyard, and I'm pretty sure that's OK under D'Antonio's policy, though water experts tell me it's not clear how to calculate what the pre-development runoff might have been. But could I capture more from the front to water the yard without running afoul of the law?
A 1968 National Research Council report on Western water had a prescient observation about the difficulties of adjusting water law to changing realities: "Laws, like dams, can be altered or removed, but with obviously greater difficulty than was associated with their creation."